1. Technical Field
The present invention relates to a light emitting device and an electronic device which include an organic electro luminescent (EL) element, and the like.
2. Related Art
An organic light emitting diode (OLED), that is, an organic electro luminescent (EL) element attracts attention as a thin light emitting source which is light in weight, and an image display apparatus including a large number of organic EL elements has been developed. The organic EL element has a configuration in which at least one layer of organic thin film formed with an organic material is sandwiched between a pixel electrode and an opposite electrode.
In a field of the organic EL element, a technique of intensifying light having a specific wavelength among emitted lights by utilizing constructive interference, or resonance has been known. With the technique, color purity of emission colors or efficiency of output light with respect to emitted light can be enhanced.
As such image display apparatuses, those disclosed in Japanese Patent No. 2797883 and JP-A-2008-218081 have been known, for example.
However, the following problems arise in the techniques disclosed in Japanese Patent No. 2797883 and JP-A-2008-218081.
That is to say, with the technique disclosed in Japanese Patent No. 2797883, light having a specific wavelength can be intensified with an action by “Micro-Optical Resonator” ((0015), (0018) and so on in Japanese Patent No. 2797883). However, means for enhancing the action, that is, means for effectively utilizing the resonance action by the optical resonator is not particularly described in Japanese Patent No. 2797883 except for the following point. That is, only an innovation relating to reflectance of a semi-transparent reflective layer is described ((0016) in Japanese Patent No. 2797883).
Further, with the technique disclosed in JP-A-2008-218081, it is considered that an effect of intensifying light having a specific wavelength with an action by an optical resonator can be also obtained ((0028) and so on in JP-A-2008-218081) as in the technique disclosed in Japanese Patent No. 2797883. However, in the technique, it is assumed that a film of a transparent electrode is formed so as to be in contact with an organic compound layer. This arises a problem that there is a large risk of causing some damage on the organic compound layer when the film of the transparent electrode is formed during a manufacturing process (see, claim 1, FIG. 1 and so on in JP-A-2008-218081). Further, it is considered that an amount of light reflection by an interface between a transparent cathode electrode 14 and an optical path length adjustment layer 15 in JP-A-2008-218081 is limited. Therefore, the resonance action by the optical resonator is not effectively utilized likely in Japanese Patent No. 2797883.